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Starting with the 2009 model year, all Weber Smokey Mountain Cookers come with a built-in lid thermometer as standard equipment. If you have a 2008 or earlier WSM, your cooker did not come with a thermometer, so you'll want to consider one of the methods described in this article for measuring cooker temperature.
Click on any of the pictures below for a larger image.
Options For Measuring Temperature
There are three primary methods for measuring temperature inside a Weber Smokey Mountain Cooker:
When I first started out with my WSM in 1997, I measured temperature using a basic kitchen thermometer inserted through the lid vent to measure temperature. These thermometers work great, cost $10-12, and can be found at hardware stores, cooking supply stores, and in mail-order catalogs. Taylor is a popular brand that you'll find in many stores. These thermometers usually include a metal clip that is used to attach the thermometer to the edge of a pot, but the clip will also suspend the thermometer in the top-most vent hole, as shown in Photo 2.
Another approach is to stick a thermometer through a cork that is inserted into one of the lid vents. Photo 3 shows a Weber #9815 Replacement Thermometer inserted in this fashion. It sells for around $15.
Several years later, I upgraded from a kitchen thermometer to an industrial-grade thermometer. These thermometers are available in a variety of stem lengths, dial sizes, and temperature ranges. They cost $40-50 and can be purchased from suppliers like Ashcroft, Tel-Tru, and Grainger. These are the thermometers you'll see mounted in expensive cookers used at restaurants and barbecue competitions.
I initially chose the Trend Model 33 thermometer shown in Photos 4-6. It has a range of 50-550°F, a 3" dial face, and a 6" stem. I drilled out the clip from my original Taylor kitchen thermometer to accommodate the Trend's larger diameter stem and reshaped it so it clipped under the edge of the top vent, as seen in Photo 6.
After a few more years, I took the plunge and drilled through the lid to mount a thermometer. Photo 7 shows how I mounted a Trend Model 33 thermometer with a shorter 4" stem in the lid, on the opposite side of the vent. See Installing A Thermometer for all the details of this process. I switched to a 4" stem so it would not touch meat placed on the top cooking grate.
Another method for measuring temperature through the lid is to hang a probe thermometer through the vent opening. Probe thermometers are described in greater detail later in this article.
A less common approach to measuring temperature in the WSM is to insert a thermometer through a hole drilled in the middle cooking section or in the access door. Owners do this in an attempt to measure temperature at the bottom cooking grate, as shown in Photo 8. The process for drilling such a hole is the same as that discussed on the Installing A Thermometer page.
One creative approach that does not require drilling is to remove the top nut and bolt from one of the grill straps and insert a thermometer through the resulting hole.
One potential problem with these approaches is that the thermometer passes through the very hot area at the outside edge of the middle cooking section, where heat flows up and around the water pan. This can result in readings higher than those measured through the lid or at the cooking grate.
There are a number of ways to measure temperature at the cooking grate. Oven thermometers come in several styles and are very affordable. The Taylor oven dial thermometer (Photos 9-10) is an example of this type of thermometer. Unfortunately, oven thermometers are not very practical for use in your smoker, because you have to open the lid to check the temperature, and every time you open the lid, you lose heat from the cooker. Oven thermometers also get covered with smoke and grease and become difficult to read.
Many people use a probe thermometer to measure temperature at the cooking grate. The Taylor probe thermometer (Photo 11) consists of a stainless steel probe attached by a long cable to a display unit that sits outside the cooker. The probe is held above the cooking surface by inserting it through a potato (Photo 12), through a block of wood or a wine cork, or by inserting it between the bones of a slab of ribs or through the corner of a brisket. (A wine cork can be whittled down and stuck into the cooking grate to hold the probe in place.) The probe cable runs under the edge of the lid or though a hole in the side of the middle cooking section. The lid will not damage the cable as long as you're gentle when replacing the lid.
One common trick with a probe thermometer is to use two different probes with a single display unit. Insert one probe in the meat and place another probe on the cooking grate, then swap the plugs back and forth on the display unit to read each temperature.
Probe thermometers will sound an alarm when cooking time or desired temperature have been reached. Some models can be set to alarm at a low temperature reading, alerting you when the fire is dying out. They're a neat gadget, sell for around $30, and are quite popular among barbecue enthusiasts. Links to some great probe thermometers can be found on the BBQ Shopping page.
Remote probe thermometers are a more sophisticated version of probe thermometer. The most popular is the Maverick ET-732 thermometer (Photos 13-15). It features two probes—one for cooker temp, one for meat temp—that connect to a radio transmitter outside the cooker. The transmitter sends temperature readings up to 75 feet to a base unit located inside your house.
For the tech-savvy barbecuer, consider the iGrill remote probe thermometer (Photo 16). It features two probes and transmits temperature readings to your iPhone, iPad, or iPod Touch via Bluetooth.
You can see more examples of how owners have installed thermometers in their Weber Smokey Mountain Cookers in the More Thermometer Installations article.
There are pros and cons to all the methods described above:
For several years I used a Taylor kitchen thermometer and a Trend industrial-grade thermometer inserted through the lid vent as the primary method for measuring temperature in my Weber Bullet. For me, this method had several advantages:
In early 2001, I decided to mount a Trend thermometer in the lid, knowing that I was trading off some of the advantages listed above for the clean, professional look of a mounted thermometer.
Most of the time, I use just the lid thermometer when cooking, but sometimes I also place a probe thermometer in the meat I'm cooking. If you do this, don't be afraid to run the cable right under the edge of the lid. You will get a little bit of smoke leakage, but it's no big deal and won't affect the performance of the cooker.
When measuring temperature through the lid, you must account for the fact that the reading will be higher than the temperature occurring at each cooking grate. I've done some "experiments" on my Weber Bullet using my Trend thermometer through the lid and a Fluke Model 52 electronic thermometer and two k-type bead probes measuring temperature 1-3/4" above each cooking grate.
My tests show that when the Weber Bullet reaches a stable temperature of 225-250°F measured through the lid, the lid temperature averages 12-15°F higher than the top grate temperature and the top grate averages 4-10°F higher than the bottom grate. These numbers assume the water pan is replenished every 90-120 minutes. So, if I'm targeting 225°F on the top grate, I'm looking for about 237-240°F on my thermometer through the lid.
When the cooker experiences a sudden temperature change (for example, when a build-up of ashes fall away from burning coals), the temperature differential between the lid and grates may fluctuate quickly and dramatically, but things will stabilize as the cooker settles back into the 225-250°F range. It should be noted that the averages described above do not hold when the cooker is running at a higher temperature, say above 280° measured through the lid, or as the cooker temperature begins to taper off as the fuel supply is exhausted.
Please consider these temperature differentials as a starting point for your own experimentation. Your temperature differential between the lid and cooking grates may be different than mine, depending on a variety of factors, including the type and accuracy of thermometer used and whether water or other media is used in the water pan.
Here are two documents you can download if you're interested in a sample of the temperature differences I've measured in the Weber Bullet, and you can read more about this subject in the WSM Temperature Tests article.
Thermometers don't maintain their accuracy forever. In fact, sometimes even brand-new thermometers right out of the package aren't accurate. That's why you should always test a new thermometer for accuracy before using it, and then retest it on an occasional basis. See Testing Thermometers For Accuracy for all the details.
WSM with two thermometers mounted: 2000 by Gary Davis.